Protection of Transmission Line in Presence of Parallel Capacitance Elements

Recently, Flexible AC Transmission System (FACTS) devices emerged to the electrical transmission line power systems and their importance increased significantly. FACTS are mainly used for enhancing power transferability and control. However, the use of FACTS introduced challenges to the transmission line protection. The protection of transmission lines depends mainly on distance protection, and adding FACTS elements have caused the protection elements to lose accuracy, reliability and security. This paper studies the sequence concept and its ability for analyzing the power system in the presence of transmission line faults and the system response to faults in both cases of FACTS absence or presence. FACTS are represented in this paper by parallel capacitance connected to the transmission lines to inject reactive power to the power system. The objective of this paper is to verify the percentage change in the fault currents, and effect on zone setting for distance protection in presence of capacitance.